No effort has been spared over the past several decades to develop the numerous modern universal cutter and tool grinding fixtures and machines which provide flexibility of operation and are adaptable to many kinds of work. In general, they are designed to hold a milling cutter in a predetermined fixed position and to apply a grinding wheel accurately to sharpen the cutter's cutting edges uniformly and provide desired clearance for the effective utilization of the cutter. It is well known that uniformity of a tool is correlatable to the lifetime of its use, that this uniformity is not attained in manually sharpened tools, and consequently automatically sharpened tools are purchased, particularly for use with numerically controlled machines, so the tools can be replaced on a regular basis to minimize downtime.
A dull cutter, especially an end mill, slows production and gives shoddy results, so it is desirable to sharpen end mills frequently. Usually this is not easily done. To sharpen an end mill easily, requires expensive machine tools beyond the means of most machine tool shops, especially the small volume ones. Typical of the sophisticated grinders used to sharpen end mills are ones disclosed in U.S. Pat. Nos. 3,719,459; 3,680,262; and 3,813,823, none of which is suitable for the use of a small machine shop operator. Manually operated grinders used to sharpen end mills, which grinders are within the economic and technological means of a small machine shop operator, are disclosed in U.S. Pat. Nos. 2,690,037; 2,958,988; 3,117,399; 3,352,068; and 3,365,843. In no practical manual grinding fixture in the prior art is it possible to observe the edges of the teeth while they are being ground.
Conventional manual grinding of end mills is generally effected in inserting the straight shank of a damaged end mill into a chuck held in a motor-driven workhead, and rotating the end mill against a rotating grinding wheel to cut-off the damaged end, then changing to a small diameter wheel (type No. 1), hollow grinding the end of the end mill, changing to a cup wheel (type No. 11) to grind the cutter clearance on the fluted ends, again changing to a 6" cup wheel (type No. 11) to grind the cutting clearance on the fluted ends, and finally grinding the secondary clearance or relief on the fluted ends. These operations are described in greater detail in available shop manuals such as one published by Covel Manufacturing Company, Benton Harbor, Mich.
Those skilled in the art will appreciate the difficulty of grinding an end mill with precision and uniformity by utilizing conventional manual methods; they also appreciate and rue the inordinate expenditure of time entailed in performing a palpably simple task. They will therefore especially appreciate the convenience and simplicity of being able to utilize a conventional, manually adjustable worktable of a fixed head grinder in conjunction with a fixture which requires only that the end mill be tiltable in a vertical plane, to obtain sharp, correctly angled cutting edges, and, that the nearly vertically held end mill be rotatable about its longitudinal axis.